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The cooling intensity of laminar cooling determines the microstructure of metal materials, thus affecting the performance of products, while the heat transfer coefficient directly affects the cooli...

Taking the dry coal shed of a coal-fired power plant as an example, the reticulated shell structure model of large-span three-centered cylindrical is established according to the specification requirements, and its design and optimization are carried out. It is to use the full stress design method to establish multiple comparison models by adjusting the thickness of the grid, to do the analysis and calculation for obtaining the comparison results of steel consumption, maximum vertical displacement and overall stability of different models, and then to determine the optimal span ratio of the large-span reticulated shell structure. All of these aim to draw relevant conclusions and provide reference for the design and optimization of similar large-span three-centered cylindrical reticulated shell engineering.

An experimental study on transient heat transfer of supercritical water during pressure variation across critical pressure in a 2 × 2 rod bundle has been carried out on the Supercritical WAter MUltiPurpose test loop II (SWAMUP-II). The bundle consists of four heated rods with an Outer Diameter (O.D.) of 10 mm and a pitch-to-diameter ratio of 1.18. The 2 × 2 rod bundle with wire wrap is installed into a square assembly box. The experimental conditions are as follows: pressure ranging from 16 to 26 MPa, mass flux ranging from 850 to 1450 kg/m 2 s, heat flux ranging from 250 to 650 kW/m 2 , inlet fluid temperature ranging from 345 to 365 °C, and depressurization/pressurization rate of 1 MPa/min. The experimental data are obtained and the transient heat transfer characteristics during pressure variation across critical pressure are discussed. The heat transfer near the critical pressure is unstable as the physical properties of water changes fiercely, and the boiling crisis is likely to occur during both pressurization and depressurization, so the pressure range from 21 MPa to critical pressure is defined as a transition pressure section. The thermal-hydraulic parameters affect the transient heat transfer alike during both pressurization and depressurization, and obviously within the transition pressure section. The boiling crisis is more remarkable and the wall temperature increment is bigger with lower mass flux, higher heat flux or higher inlet fluid temperature. In order to avoid boiling crisis within the transition pressure section, the mass flux should be increase to or kept at higher level, the heat flux should be kept at or reduced fast to lower level, and the flow boiling should be kept at subcooled boiling.

Fully bio-based polyamide 1010 (PA1010) was successfully melt-blended with poly (vinyl alcohol) (PVA03, PVA05, PVA08 and PVA14) to prepare PA1010xPVAzy blends. The PA1010xPVA03y, PA1010xPVA05y, PA1010xPVA08y and PA1010xPVA14y films demonstrated the lowest oxygen transmission rates (OTR), free volume fraction (Fv), mean volume of the free volume holes (Vf) and mean number of free volume holes per unit volume (I3) values, when the PVA concentration in each PA1010xPVAzy series reached a corresponding critical value of 22.5, 20, 17.5 and 12.5 wt%, respectively. OTR, Fv, Vf and I3 values obtained for the best PA101087.5PVA1412.5, PA101082.5PVA0817.5, PA101080PVA0520 and PA101077.5PVA032.25 films reduced gradually as the degree of polymerization of PVA reduced. The results of dynamical mechanical and other experimental characterizations demonstrated that PA1010 and PVA are compatible to some extent, when the PVA are ≤ the corresponding critical concentration. The significantly enhanced oxygen permeation resistance and free volume characteristics for optimal PA1010xPVAzy films is at least partly due to the improved hydrogen-bonded molecular interactions between PA1010 C=O groups and PVA O-H groups.

Experimental studies on heat transfer to supercritical water in 2 × 2 rod bundle with wire wraps are performed at Shanghai Jiaotong University. The test section consists of two channels separated by a square steel assembly box with round corners. Water flows downward in the first channel and then turns upward in the second channel to cool the 2 × 2 rod bundle with wire wraps installed inside the assembly box. The bundle consists of four heater rods of 10 mm in O.D. and 1.18 in. pitch-to-diameter ratio. Experimental parameter ranges cover pressure from 23.0 MPa to 26.0 MPa, mass flux from 400 kg/m 2 s to 1400 kg/m 2 s, heat flux from 300 kW/m 2 to 1000 kW/m 2 and bulk temperature from 280 °C to 500 °C. The fluid enthalpy in the first channel increases due to the heat transfer through the assembly box when flowing downward. Heat transfer deterioration is observed in the bundle. The degree of the deterioration is moderated in the developed region due to the mixing by the wire wraps. Significant non-uniformity of circumferential wall-temperature distribution around the heater rods is observed. Effects of various parameters on heat transfer behavior inside the 2 × 2 rod bundle are similar to those observed in a tube. The heat transfer enhancement due to the wire wraps becomes remarkable under a high mass flux condition. The Jackson and Fewster correlation and Bishop et al. correlation give the best predictions when evaluated against the experimental data.

Oxygen transmission rates and free volume properties (i.e. average volumes of free-volume-cavities (Vf), mean number of the free volume cavities per unit volume (I3) and fractional free volume (Fv)) values of bio-based polyamide 612 (PA612)/poly(vinyl alcohol) (PVA) (i.e. PA612xPVA03y, PA612xPVA05y, PA612xPVA08y and PA612xPVA14y) blend films were reduced to a minimum value, when their PVA content reached corresponding optimal values of 25, 20, 15 and 10 wt%, respectively. The minimum oxygen transmission rate, Vf, I3 and Fv value obtained for the best PA61290PVA1410, PA61285PVA0815, PA61280PVA0520 and PA61275PVA0325 bio-based blown films reduced considerably with decreasing PVA degrees of polymerization. As evidenced by the results of dynamical mechanical analysis, differential scanning calorimetry, wide angle X-ray diffraction and Fourier transform infrared spectroscopic experiments, PA612 and PVA are miscible to some extent at the molecular level when their PVA contents are ≤ the corresponding optimal values. The significantly improved oxygen barrier and free volume properties for the PA612xPVAzy blend films with optimized compositions is at least in part to the enhanced intermolecular interactions between PA612 carbonyl groups and PVA hydroxyl groups.

The polishing process was optimized according to the polishing rate and its consistency of HE slurry with different dilution multiple on the copper wafers, it can be confirmed that: the best pressure value of HE1, HE10, HE20, HE50 type slurries was 6890Pa, the best flow rate value of the preceding three slurries was 300ml/min, the best value of the HE50 slurry was 400ml/min. Through the planarization effects of the slurries with different dilution multiple, it can be obtained that: the initial dishing and erosion heights of the samples were both 1270nm and -500nm, and the two values respectively changed to 539.3nm, -75.7nm and 796.3nm, -191.3nm after being treated by HE1 and HE10 slurries, the step height of the wafer changed from 117nm to 72nm after being treated by HE20 slurry, the step height of the wafer changed from 88nm to 71nm after being treated by HE50 slurry. It was concluded that: the HE slurry shows strong ability for step removal when the slurry is diluted by 1 times and 10 times, the HE slurry also owns high planarization ability when the slurry is diluted by 20 times and 50 times.

Purpose– The purpose of this paper is to build a transient wear prediction model of surface topography of textured work roll, and then to investigate the wear performance of different original textured surfaces. The surface topography of steel sheets is one of the most important surface quality indexes, which is inherited from the textured work rolls in cold rolling. Surface topography of work roll is obviously changing in the cold rolling process. However, surface topography is difficult to measure in the industry production process.Design/methodology/approach– This paper presents a numerical approach to simulate the wear process based on the mixed lubrication model of cold rolling interface developed by Wilson and Sheu (Sheu and Wilson, 1994). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the volume is removed by an abrasive particle which is an abstract concept based on the wear phenomenon of textured work roll. At each simulation cycle, the distribution of the contact pressure is calculated by the lubrication model. The material is removed by an abstract abrasive particle and the surface topography is modified correspondingly. The renewed surface topography is then used for the next cycle.Findings– Through comparative analysis, it can be found that the simulation results possess similar statistical characteristic with the measured data. A set of roughness parameters such as the amplitude, spacing and frequency-domain characteristics are introduced to analyze the wear performance of different textured surfaces. Numerical examples show that the surface topography has a significant effect on the wear performance of work roll in cold rolling.Originality/value– The proposed model can accurately predict the wear process of the surface topography in the cold rolling process, which provides the foundation for optimization of original surface topography of textured work roll. The model can also be considered as a tool applicable for research on control of the surface topography of steel strip in the cold rolling process.

There is an electrical stimulation device for dental implant healing, which is designed for dental patients who have been received an implant in their jaws during the three months of healing period. The device consists of adjustable constant current (or constant voltage) circuit, power supply (including DC or external AC power supply and transformer), MCU(Microcontrollers), wire and electrode, electrode fixed and connecting device, control panel and shell. When the dental implants have been implanted, the instrument facilitates osseointegration between the implant and the alveolar bone and healing of the implant and gingival tissue. There is the most advantage that we can adjust the corresponding constant voltage (50-1000mV) or constant current (10-200mA)and the loading time(10-60min) depending on the patient's alveolar bone condition.

Plastic materials are widely used in automobile manufacturing, and they have different mechanical characteristics at high and low temperature, which has a major influence on automobile safety. This paper mainly studies the relationship between elastic modulus and yield strength of plastic materials at high and low temperature, in order to predict the elastic modulus by the yield strength. On this basis, the values of the parameter of the constitutive model will be predicted to obtain the constitutive equation. The method meeting the precision is validated by the experiments. The method decreases experimental working, and provides technical support for product development as well.

For 300 MW inner cooling turbo generator, a discrete model for cooling material flow distribution of radial ventilation cooling system has been developed. The structure optimization is studied with this model. The effect of the radial distance and the tangential distance on stator’s radial flow distribution was analyzed and optimized. The results of the simulation show that with the same inlet-outlet flow pressure the flow deviation increased as the radial distance increased but the tangential distance decreased oppositely.

The mechanical behavior of plastic material is dramatically sensitive to temperature. An method is proposed to predict the mechanical behavior of plastics for cars, ranging from low-temperature low temperature ≤-40°C to high temperature ≥80°C. It dominates the behavior of plastic material based on improved constitutive model in which the parameters adjusted by a series of tests under different temperatures. The method is validated with test and establishes the basis for research and development of plastic parts for automobile as well.

In this paper, research the hypereutectic high chromium cast iron by the methed of semi-solid method for cooling inclined plate. Influence of cooling rate on size of primary carbides and mechanical property of hypereutectic high chromium cast iron. The results showed that, speed up the cooling speed can effectively refine eutectic primary carbides in hypereutectic high chromium cast iron. The primary carbides was globularity and slug, provided with excellent mechanical properties. But when the cooling speed is too fast, the pouring temperature is too low, so that the liquid metal has high viscosity, poor mobility. there were a small amount of inclusions in the Preparation of casting. Although still generate pieces of fine carbides in the matrix, but the distribution is not uniform. disadvantage of the comprehensive performance.

This paper investigates the effects of surface spacing parameters on mixed lubrication based on a full numerical solution proposed by Hu and Zhu. Sinusoidal wavy surfaces with identical Ra and bearing area curve (BAC) but entirely different peak count ( Pc) are chosen to substitute the real textured engineering rollers surface. A set of mixed lubrication parameters such as average lubrication film thickness, ratio of contact area, ratio of contact load, and non-dimensional maximum pressure are introduced to analyze the effect of spacing parameters of surface on mixed lubrication performance. Numerical examples show that the spacing parameters have a significant effect on the contact parameters. That would be helpful for optimizing the textures, which are engineered into rollers surface for lubrication and wear performance improvement.

Objective: To evaluate the influence of three pattern materials on the marginal fitness of Co-Cr alloy inner crown of porcelain fused to metal (PFM) endocrown. Method: Standard molar abutments mould with 90°shoulder, 6°convergens, 5.0mm occlusal-gingival height, and 15.0mm neck diameter were made of stainless steel. Three kinds of pattern materials, including Inlay wax (group A), Casting Pattern resin (group B), and Pattern Resin (group C), were used to fabricate the pattern of Co-Cr alloy inner crown of PFM endocrown. The fitness of the inner crown finished was evaluated. T test was used for statistical analysis. Results: The means of marginal gaps between inner crown and abutment shoulder made of three pattern materials were 55.9μm for group A, 37.1μm for group B, 63.1μm for group C respectively. There were statistically significance among the 3 groups (P< 0. 05). Conclusion: As a pattern material, Casting Pattern resin is suitable for fabrication of Co-Cr alloy inner crown of porcelain fused to metal endocrown.

The aim of this study is to investigate the effect of SiC particle pretreatment, aluminum matrix particle size and sintering temperature on relative density, hardness, microstructure and wear resistance to SiC particle einforced aluminum matrix composites. To this end, the amount of 16.7 wt.% SiC with average particle sizes 20μm was used along with pure aluminum of average particle size of 75 μm and 25μm. Powder metallurgy is a method used in the fabrication of this composite in which the powders were mixed using a planetary ball mill. By analyzing SEM micrograph and the Property test, it is concluded that SiC particle pretreatment has significant effect on the morphology of pecimens. pretreatment increase the interface adhesion, improve the wettability. SiC is uniformly distributed in the matrix, with good relation to the substrate, the maximum hardness is 51.1HB, the minimum wear rate is 0.1684%, while the density is 97.3%.For the same SiC content and particle size, the smaller the particle size of aluminum matrix is, the higher wear resistance of composite materials is on condition that others are same, the higher sintering temperature and the higher the wearability of composites, the wear resistance of the composite material is significantly improved after SiC pre-processing.The relative density increases with increasing aluminum matrix particle sizes under the same pressure and the holding time. The actual density of all samples reached the theoretical density over 96%, to a maximum of 98.9%.

mi-rigid base on crack resistance, using orthogonal experimental design method, arranged 16 groups of orthogonal test and conducted the water content test and drying shrinkage test that aimed at various ages from 5d to 50d respectively. The results indicated that with the increasing of waste asphalt content, the shrinkage gradually increasing and the maximum reached when the dosage of waste asphalt concrete was 55%, since then, with the increasing of waste asphalt content, the shrinkage gradually decreasing and the range was largely. Fiber has little effect on moisture loss and shrinkage, with the increasing of fiber content, the moisture loss of materials with different ages increased gradually and the maximum loss rate reached when the dosage of fiber was 4, then the moisture loss decreased gradually after that. As for shrinkage, it reached minimum value when the dosage of fiber was 2.5. Mixing waste asphalt concrete and fiber in reasonable dosage can improve the crack resistance of materials.

The tempering temperature on microstructure and mechanical properties of 35CrMnSiMo cast steel are studies in this article. Results showed that 880°C×30min 35CrMnSiMo cast steel after quenching water, hardness up to 49.6HRC, reached 39.04 J/cm2 toughness. Tempering temperature selected 200°C, 400°C and 600°C, respectively with the increase of the tempering temperature plummeting hardness and impact toughness are on the rise, but at 400°Cdecreased. Photos can be seen from your organization after quenching, which contains a lot of lath martensite, a small amount of lump some residual austenite and martensite, 200°C tempering martensite has been reduced, some of carbide precipitation into tempered martensite. Tempering of martensite quenching slats or flake, it is made of flake martensite and small ξ carbide distribution.

This paper mainly studied the high temperature quenching oil quenching, tempering temperature on the influence of high strength steel mechanical properties of wear resistant. The results show that high strength and toughness wear-resistant cast steel with 880°C× 30min after oil quenching, the hardness of 38.6HRC steel, the impact toughness value reaches 40.18J/cm2. After 200°C, 400°C and 600°C tempering, with the increase of the tempering temperature, the hardness decreased linearly, as by 600°C tempering, the hardness has been reduced to 22.3HRC. Impact toughness with the tempering temperature, the overall upward trend, the impact toughness of some reduced at 400°C, the highest impact toughness value reaches 113.34J/cm2. From the fracture morphology can be seen, with the increase of tempering temperature, ductile fracture increased, by 600°C tempering is dimple fracture, obviously can not see the traces of brittle fracture.

Fine zirconium diboride (ZrB2) powders with high purity were successfully prepared by combustion synthesis through magnesiothermic reduction process in Mg–B2O3–ZrO2 system. The reaction mechanism was investigated by differential thermal analysis and quenching experiment. The results show that the whole magnesiothermic reduction process includes three stages: first, molten B2O3 and Mg formed above the temperature of 650 °C, and glassy B2O3 and solid ZrO2 particles were coated on the surface of the molten Mg; thus, the hollow balls can be formed when the molten Mg was exuded under capillary function. Second, ZrO2 particles reacted with molten Mg to form Zr and MgO with dissolution–precipitation mechanism, which released a large amount of heat to induce the diffusion reaction between B2O3 and Mg to form B and MgO. Last, Zr reacted with B to form ZrB2 grains. The preparation of ZrB2 by self-propagating synthesis in Mg–B2O3–ZrO2 system is a solid–liquid-liquid reaction.

In this article, the authors use of Si, Mn, Cr as the main alloying element, developed a tough wear resistant cast 35CrMnSiMo, after casting, to obtain a wear-resistant cast steel with a hardness and impact toughness mechanical performance testing, metallurgical microscope and scanning electron microscope analysis of the microstructure. The results show that, the cast 35CrMnSiMo 850 °C austenitizing insulation 30min and then quenched, the material water hardened degrees is much larger than the oil hardened degrees. The the water hardened than oil hardened degrees up 28.5%. Metallographic photo clearly see a lot of lath martensite, the small amount of lath martensite and retained austenite, the oil quenching microstructure edge outline is somewhat vague, while clear the water quenching microstructure edge contour darker, impact toughness with hardness is inversely proportional to the sample.

This paper mainly through the experimental study on the heat treatment process and mechanical properties of cast steel 35CrMnSiMo.According to the effect of alloy elements in design of a high-toughness abrasion-resistant cast steel, Cr, Mn, Si, as the main alloy elements, supplemented by a small amount of Mo, the casting molding, for hardness and impact toughness test of mechanical properties of experimental steel. The results show that, the as-cast 35CrMnSiMo by 880 °C, quenching for 20min then, the same quenching temperature, quenching hardness of materials is far greater than the oil quenching hardness. Water quenching hardness up to 25% higher than the oil quenching hardness, The impact toughness of specimen is inversely proportional to the contrast relationship Hardness.

Columnar crystaldendriteequiaxial dendritescolumnar crystalNanosized powder was synthesized by direct-reactive precipitation process using a stoichiometrical mixture of TiCl4, BaCl2 as the reactants while NaOH as precipitant. Under the ratio of Ba to Ti is 1.02, PH=13, three reaction temperature of 70°C, 80°C and 90°C were conducted respectively. Morphology and phase structure of powder were investigated, and the influence of reaction temperature on powder morphology was discussed. The result indicates that synthesized powder is single cubic BaTiO3 and contains no impurities. BaTiO3 powders generally show spherical, and average particle size decreases with increasing reaction temperature. When reaction temperature is 80°C, BaTiO3 powder has best uniformity and dispersivity with the diameter of 80-100nm. The influence of reaction temperature on powder particle size can be attributed to the corporate contribution of nucleation and growth rate. Polyglycol as surface active agent has a significant effect in restraining agglomeration.

Nitrogen-doped TiO2 nanotubes (N-TNTs) were fabricated on the titanium foil by anodic oxidation and followed by annealing at NH3 environment. Highly ordered nanotubes, roughly 150 nm in the diameter and 20 μm in the length, were synthesized on the titanium foil. By controlling oxidation voltage, the thick TiO2 nanotubes were peeled off from the titanium substrate. In one step annealing at NH3 environment, nitrogen replaced oxygen and doped into TiO2, but anatase phase was formed.

Hard PZT (PZT4)-based composites embedded by ZnO nanoneedles (denoted as PZT/ZnOn) were fabricated by a solid state sintering technique. The characteristic diffraction peaks of the perovskite PZT and ZnO phases were identified from the studied composites, indicating the retention of ZnOn. With increasing ZnOn content, the grain size of the composites was reduced gradually. In contrast with the pure PZT, the PZT/ZnOn composites possessed more excellent mechanical properties, while the piezoelectric properties were reduced by a certain extent. The best mechanical properties of PZT/ZnOn composites were obtained by sintering at 1,150 °C with 1.5 wt% ZnO nanoneedles addition: fracture toughness K IC ~ 2.04 MPa m1/2, flexural strength σ f ~ 105.44 MPa, compressive strength σ c ~ 543.89 MPa. The piezoelectric properties of the PZT/ZnOn composites were found to be lower than that of the pure PZT with dielectric permittivity e r of 768–893, piezoelectric coefficient d 33 of 240–260pC/N, mechanical quality factor Q m of 340–650 and planar electromechanical coupling k p of 0.5–0.55.

Lead is a cumulative toxicant, which can induce severe health issues, especially in children’s case due to their immature nervous system. While realizing large-scale monitoring of children blood lead remains challenging by utilizing traditional methods, it is highly desirable to search for alternative techniques or novel sensing materials. Here we report a label-free and portable aptasensor based on graphene field effect transistor (FET) for effective children blood lead detection. With standard solutions of different Pb2+ concentrations, we obtained a dose-response curve and a detection limitation below 37.5 ng/L, which is three orders lower than the safe blood lead level (100 μg/L). The devices also showed excellent selectivity over other metal cations such as, Na+, K+, Mg2+ and Ca2+, suggesting the capability of working in a complex sample matrix. We further successfully demonstrated the detection of Pb2+ ions in real blood samples from children by using our aptasensors and explored their potential applications for quantification. Our results underscore such graphene FET aptasensors for future applications on fast detection of heavy metal ions for health monitoring and disease diagnostics.

Cylindrical shells are widely used in civil engineering. Examples include cooling towers, nuclear containment vessels, metal silos and tanks for storage of bulk solids and liquids, and pressure vessels. Cylindrical shells subjected to non-uniform wind pressure display different buckling behaviours from those of cylinders under uniform external pressure. At different aspect ratios, quite complex buckling modes occur. The geometric nonlinearity may have a significant effect on the buckling behavior. This paper presents a widely study of the nonlinear buckling behavior of cylindrical shells of uniform thickness under wind loading. The finite element analyses indicate that for stocky cylinders, the nonlinear buckling modes are the circumferential compression buckling mode, which is similar to cylinders under uniform external pressure, while for cylinders in mediate length, pre-buckling ovalization of the cross-section has an important influence on the buckling strength.

The existing research on flange focused on bearing capacity, and there were few reports on the rigidity of flange. In this paper, rigidity test was carried on for the connection of rigid flange and flexible flange in power-transformed frames. According to the test results, the axial rigidity, shear rigidity and flexural rigidity was compared. The results indicated that the axial rigidity, shear rigidity and flexural rigidity of flexible flange connection was lower than those of rigid flange connection for both the plain bolt and high strength bolt.

Test items include compressive strength, anti-breaking strength and split strength of standard concrete, rubber concrete and fiber-rubber concrete, and 43 groups test were conducted. In order to investigate the influence of the synergistic reaction between fiber and rubber powder on force-bearing performance of concrete used in subgrade, and different blended ratio effect on strength and extension of concrete were studied. The results indicated that with the increasing of content of 40 mesh rubber powder, the compressive strength of concrete decreasing regularly; with adding the blends of fiber and rubber powder, the anti-breaking strength and extension of concrete were promoted, as to fiber - 40 mesh rubber powder concrete, the content of rubber control less than 6%, and the fiber less than 0.5%，as to 60 mesh rubber powder -10mm fiber concrete, the content of rubber control less than 6%, and the fiber less than 0.5%; as to 60 mesh rubber powder -20mm fiber concrete, the appropriate adding quantity of rubber less than 2%, and the fiber less than 0.5%.

Four different types of full-scale slotted end plate (SEP) connection joints are tested to determine their failure modes and damage mechanisms under ultimate load, also analyze their force-displacement behaviors and developing processes of deformation and stress. The results show that ultimate bearing capacity of the I-type SEP joint is only approximate 1/2 of the other three types of SEP joints, which indicate the SEP’s type have great influence on the ultimate strength of joints. The instability of SEP is the main factor to cause the loss of bearing capacity of the connection joints, which is shown through the development of stress, that SEP enters into plastic stage and the other regions still are elastic.

Based on the experiment,the forming properties of Aluminum alloy in liquid forging was studied by adding rare-earth metal Y (Yttrium) modificatior and ternary modificatior(25% NaF +62% NaCl +13% KCl).The structure and mechanical properties of the prepared samples under two modifications were compared.The results showed that the rare-earth metal Y can modificatior liquid aluminum alloy forging a comprehensive mechanical properties of a substantial increase, the use of rare-earth metal Y (Yttrium)modificatior was better than ternary modificatior.

According to Cr-Ni stainless steel, three different welding technology and the appropriate welding process parameters were selected. Three welded joints of Cr-Ni stainless steel were prepared. The microstructure in weld metal zone of Cr-Ni stainless steel under different welding methods was studied by X-fluorescent chemical composition analysis and microstructure analysis. The results show that alloy composition of the weld metal are different and distribute unequally under different welding methods, microstructure morphology and grain size of the weld layer are quite different. the structure of bottom is small amount of γ phase and a little δ phase are combined together and cover is γ phase and Cu-wealthy phases in the welds under TIG-MAG welding. the structure of bottom is coarse columnar crystal and cover is typical cellular dendrite in the welds under TIG- TIG welding. the structure of bottom is tiny equiaxial dendrites and columnar crystal and cover is some γ phase and a little δ phase are combined together in the welds under TIG-SMAW welding.

Flange connection has been applied widely, and many researches have been done on flange connection both at home and abroad. But the existing research on flange focused on bearing capacity, and there were few reports on the rigidity of flange. In this paper, rigidity test was carried on for the connection of rigid flange and flexible flange in substation frameworks. According to the test results, the tensile rigidity, shear rigidity and flexural rigidity was compared. The results indicated that the tensile rigidity, shear rigidity and flexural rigidity of flexible flange connection was lower than those of rigid flange connection with high strength bolts.

By way of alloying, a sort of low-chromium heat-resistant ductile iron material was developed. Through the observation of microstructure, testing of mechanical properties and process performance, heat-resistant test, the microstructure and properties of heat resistant ductile iron of low chromium was studied. The results show that microstructure of the developed heat-resistant ductile iron is spherical graphite distributed regularly on matrix of pearlite and a small amount of ferrite; mechanical properties, processing performance and high-temperature heat resistance of samples of different chrome composition are preferable, but 1.6% of chromium component possess the best performance.

AZ31B magnesium alloys recycled by solid-state process from oxidized chip were extruded repeately. Microstructures and mechanical properties of recycled alloys for different extrusion times were studied. With the increasing extrusion times, the breaking degree and homogeneity of oxide increase and stream line feature of oxide become less obvious. Second extrusion make dynamic recrystallization microstructure of recycled alloy become more homogeneous and fine, but the microstructure is not refined furtherly after 3 and 4 times extrusion. The ultimate tensile strength increases with the increasing extrusion time, which resulting from the microstructure evolution during repeating extrusion and the enhanced bonding between oxide and magnesium alloy matrix. The elongation to failure of recycled alloy increases after second extrusion and continuously decreases after 3 and 4 time extrusion. This is determined not only by the variation of dynamic recrystallization microstructure and bonding strength between chips but also by the distribution status of oxide.

Nb2O5-modified PZT/ZnO nanowhisker (denoted as PZT/ZnOw–Nb2O5) piezoelectric composites were prepared by a solid state sintering technique. Effects of Nb2O5 addition on the microstructure, electrical, and mechanical properties of the PZT/ZnOw composites were investigated. With increasing Nb2O5 content, the grain size of the composites was reduced and the fracture mode changed from intergranular to intragranular gradually. Compared with the PZT/ZnOw composites, the dielectric, piezoelectric, and ferroelectric properties of the PZT/ZnOw–Nb2O5 composites were improved significantly, while mechanical properties were enhanced slightly. The optimum electrical and mechanical properties were achieved for the PZT/ZnOw composites modified with 0.75 wt% Nb2O5 sintered at 1150 °C, with dielectric permittivity er, piezoelectric coefficient d 33, planar electromechanical coupling k p, remnant polarization P r, fracture toughness K IC, and flexural strength σf being on the order of 4930, 600 pC/N, 0.63, 29.2 μC/cm2, 1.56 MPa m1/2 and 130 MPa, respectively. The Nb2O5-modified PZT/ZnOw piezoelectric composites, with comparable electrical properties and improved mechanical properties than those of commercial PZT-5H ceramics, are promising candidates for further applications.

The flow stress at the temperature of 250~450°Cand different strain rate of casting AZ91D magnesium alloy was studied through experiment, which adopting the Gleeble 3500 system of DSI company. The mathematical model of flow stress containing the softening factor which is suitable for casting AZ91D magnesium alloy was proposed. The temperature and strain rate conditions during full dynamic recrystallization were found by observing the microstructure.

Bamboo is a typical natural fiber-reinforced composite material with superior mechanical properties. As the reinforce phase in bamboo composite, the vascular bundles were extracted from different height locations of a Moso bamboo with an alkali treatment method, and the mechanical properties were investigated via the tensile test. It is found that both the longitudinal Young’s modulus and strength of the vascular bundles are linearly increased from the inner to outer side. To study the variation of mechanical properties of bamboo culm along the radial direction, thin bamboo slices were also tested. Using a modified rule of mixtures, the longitudinal Young’s modulus of bamboo slices are analyzed and excellent agreement can be found between experimental and theoretical results, which indicates that the longitudinal Young’s modulus of bamboo culm is cubically increased in the radial direction.

Lead zirconate titanate (PZT) based piezoelectric composites embedded with ZnO nanowhiskers (ZnO w ) were investigated to clarify the optimal sintering condition for densification, microstructure, and electrical properties. The samples are characterized by X-ray diffraction analysis and scanning electron microscopy. The results show that the increase of the sintering temperature and time is quite effective in improving the densification and piezoelectric properties of the PZT/ZnO w composites. However, the relative density and piezoelectric properties deteriorate as the composites are sintered over the optimal sintering condition. Particularly, the PZT/ZnO w composites sintered at 1150 °C for 2 h show excellent electrical properties of piezoelectric constant d 33 ∼ 471 pC/N, relative dielectric constant ɛ ∼ 3838, planar electromechanical coupling factor k p ∼ 0.543, remnant polarization P r ∼ 23.2 μC/cm 2 and coercive field E c ∼ 9.2 kV/cm.

New lead zirconate titanate/zinc oxide nanowhisker (PZT/ZnOw) ceramics were fabricated by a conventional solid state processing and their structures, piezoelectric, ferroelectric and mechanical properties were studied. Both the PZT perovskite and ZnO phases can be observed from the X-ray diffraction patterns. The grain size of ceramics is reduced due to the ZnOw addition. The incorporation of ZnOw into the PZT ceramics improves the strength and toughness, while deteriorates the piezoelectric and ferroelectric properties. For the PZT/ZnOw ceramics with 1–2 wt% ZnOw, the mechanical properties become optimum, meanwhile maintain good piezoelectric and ferroelectric properties: σc = 376–484 MPa, σf = 115–121 MPa, KIC = 1.41–1.54 MPa m1/2, d33 = 442–490 pC/N, kp = 0.54–0.55, er = 3,322–3,980, Qm = 99–101, tanδ = 1.6%–1.7%, Pr = 21.5–26.9 μC/cm2 and Ec = 8.1–8.6 kV/cm.

The addition of ZnO nanowhiskers (ZnOw) in lead zirconate titanate (PZT) matrices results in reinforced composite materials but deteriorates their electrical properties. In this study, novel piezoelectric PZT/ZnOw composites modified with Nb2O5 were successfully fabricated using solid-state sintering method. The experimental results showed that the addition of 0.5 wt% Nb2O5 resulted in highly dense and homogenous PZT composites after sintering at 1150°C, with good piezoelectric and ferroelectric properties similar to pure PZT, specifically piezoelectric constant d33=665 pC/N, electromechanical coupling factor kp=0.7, relative dielectric constant ɛ=5048, and remnant polarization Pr=30.2 μC/cm2. The “soft effect” of Nb5+ ions, reflected in the improvement of the aforementioned properties, is attributed to the accommodation of Nb5+ ions at the B sites of the lattice of PZT. Compared with the PZT/ZnOw reinforced composites, the mechanical properties were slightly improved by adding 0.5 wt% Nb2O5, where flexural strength σf of 128 MPa and fracture toughness KIC of 1.46 MPa·m1/2 were measured.

Bamboo is a typical natural fiber reinforced composite material with superior mechanical strength and toughness. As a typical hierarchical material, the macroscopic properties of bamboo are determined by its microscopic structure. The vascular bundles are the reinforce phase in bamboo composite. There was little research on the variation of mechanical properties of bamboo vascular bundles. In this work, the mechanical properties of Moso vascular bundles along the axial direction were investigated by tensile test. It is shown that the longitudinal Young’s modulus and strength of the Moso vascular bundles are linearly increased from inner zone to outer surface.

Both experimentation and calculation of the Yada model modulus of casting AZ31 magnesium alloy are provided in this paper. Based on revised Yada model, the microstructure simulation of precision forming inner gear is performed using Superform software. On the basisi of result analysis, the microstructure transformation of the casting magnesium alloy in the hot-forming process is forecasted in terms of revised Yada model.

Hydroxyapatite coating on metal implants is an effective method to enhance bioactive properties of the metal surface. We report here a method to coat the Ti-6Al-4V alloy with hydroxyapatite crystals. After alkaline/heat treatment, the spontaneous growth of organoapatite on titanium alloy surface involves sequential preadsorption of titanium isopropoxide (TIPO) and the copolymer of acrylic acid and itaconic acid on the metal, followed by exposure to simulated body fluid (SBF). The organoapatite characterization of the coating was carried out by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. The copolymer of acrylic acid and itaconic acid overlayer which is rich of carboxylate groups can lead to the deposition of needle-like and homogeneous HA on the surface after immersion in SBF.

Chitosan fibers(CSf) andCaSiO3 were incorporated into a poly (L-lactic acid)/hydroxyapatite (PLLA/HA) matrix as reinforcements to prepare scaffold composites with adequate strength and high porosity for bone tissue engineering combined with emulsion freeze drying technique. The structural morphology of the composites was observed by scanning electron microscope (SEM). The porosity was tested by liquid substitute method. The mechanical property was measured. The effects of addition of CSf and CaSiO3 on composites were also discussed. Simulated body fluid (SBF) experiments were conducted to assess the bioactivity of the composites. The chemical components of resultants on surfaces after the immersion in SBF were analyzed by fourier transform infrared spectroscopy (FTIR). The results show that the composites with high connectivity have pore sizes of 100~250μm, a porosity of 60%~80%, compressive strength of 3.5~8.0MPa. In the SBF tests, Chitosan fiber reinforced PLLA/HA-CaSiO3 composite degraded stably, meanwhile, the formation of a layer of bone-like apatite on the surfaces of the samples indicated a good bioactivity. Studies suggest the feasibility of using CSf reinforced PLLA /HA-CaSiO3 composite for bone tissue engineering.

A novel kind of denture base nanocomposite was prepared by polymethyl methyacrylate(PMMA) and cethyltrimethylammonium bromide modified organic montmorillonite (OMMT). The dispersion of montmorillonite in the polymer matrix was characterized by x-ray diffraction (XRD) and transimission electron microscope (TEM).The content of residual MMA in nanocomposites and the amount of MMA released to water from nanocomposites were determined by gas chromatography (GC). The analysis of TEM and XRD showed that exfoliated-intercalated and intercalated nanocomposites were formed when the content of OMMT was 3% and 5% in the PMMA powder respectively. The results of GC showed that the residual MMA increased with the increase of OMMT content in the polymer matrix. After 7 days in water, the amount of MMA released into water from the nanocomposites tended to be stable. The results of one-way ANOVA and t-test showed that OMMT gave a significant increase of residual MMA concentration (p